Islam permits cousin marriage. Cousin marriage was prevalent in ancient arabia and later it has become widespread among muslims because of tacit support in Islamic doctrine.

Islam's prophet Muhammad himself hoped to marry his first-cousin Fakhitah (later better known as Umm Hani), who was the daughter of his uncle (father’s brother) Abu Talib and the elder sister of Ali. To his disappointment Abu Talib refused permission, and Umm Hani was married off to a maternal cousin instead. After the death his first wife Khadijah, Muhammad married other women, including two of his own cousins, both daughters of his father’s sisters – Umm Salamah (the daughter of his aunt Atikah), and Zaynab bint Jahsh (the daughter of his aunt Umaymah). Umm Salamah was his 6th choice of wife, and Zaynab his 7th.

Muhammad's own daughters all married cousins for their first husbands. Zaynab married a maternal cousin, his daughters Ruqaiyyah and Umm Kulthum married the sons of his paternal uncle Abu Lahab, and his daughter Fatimah married her second-cousin Ali, the son of his paternal uncle Abu Talib.

Marrying close relatives such as cousins is considered act of incest in many cultures throughout the world. In addition to that, offsprings produced in this kind of marriage have high chance of death and genetic disorders.

The problem persists predominantly in muslim communities where cousin marriage is frequent and prefered.